Steps to reproduce

Specs with conditional language dependencies, like hdf5, fail concretization if the input spec imposes a conditionally activated language:

$ spack spec hdf5 %cxx=gcc

They succeed if the variant is activated manually:

$ spack spec hdf5+cxx %cxx=gcc

Error message

$ spack spec hdf5 %cxx=gcc
==> Error: internal solver error: the following specs were concretized, but do not satisfy the input:
    - input: hdf5 %cxx=gcc
[ ... ]

Information on your system

• Spack: 1.2.0.dev0 (499a1b5)
• Builtin repo: spack/spack-packages@e6dbe84
• Python: 3.13.2
• Platform: linux-ubuntu20.04-icelake

General information

• I have run spack debug report and reported the version of Spack/Python/Platform
• I have searched the issues of this repo and believe this is not a duplicate
• I have run the failing commands in debug mode and reported the output